Rupture process of the 2021 M7.4 Maduo earthquake and implication for deformation mode of the Songpan-Ganzi terrane in Tibetan Plateau

The deformation mode of the Tibetan Plateau is of crucial importance for understanding its construction and extrusion processes, as well as for the assessment of regional earthquake potential. Block motion and viscous flow models have been proposed to describe the deformation field but are not fully...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 119; no. 23; p. e2116445119
Main Authors Yue, Han, Shen, Zheng-Kang, Zhao, Zeyan, Wang, Teng, Cao, Bonan, Li, Zhen, Bao, Xuewei, Zhao, Li, Song, Xiaodong, Ge, Zengxi, Ren, Chunmei, Lu, Weifan, Zhang, Yong, Liu-Zeng, Jing, Wang, Min, Huang, Qinghua, Zhou, Shiyong, Xue, Lian
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 07.06.2022
Subjects
Anisotropy
Compression
Deformation
Earthquakes
Extrusion
Fault lines
Geological faults
Mountains
Paleoceanography
Physical Sciences
Rupture
Rupturing
Seismic activity
Shear deformation
Tectonics
Viscous flow
Tibetan Plateau
Tibetan Plateau
seismic anisotropy
deformation mechanism
Songpan-Ganzi terrane
Maduo earthquake
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Summary:The deformation mode of the Tibetan Plateau is of crucial importance for understanding its construction and extrusion processes, as well as for the assessment of regional earthquake potential. Block motion and viscous flow models have been proposed to describe the deformation field but are not fully supported by modern geophysical observations. The 2021 Mw 7.4 Maduo earthquake, which occurred inside the Songpan-Ganzi terrane (SGT) in central-east Tibet, provides a chance to evaluate the associated deformation mode of the region. We conduct a joint inversion for this earthquake and resolve a bilateral rupture process, which is characterized by super- and subshear rupture velocities, respectively. We interpret this distinct rupture behavior to be the result of the respective slip concentration depths of the two ruptured segments. We analyze geological, seismic, and geodetic evidence and find that the SGT upper crust shows distributed shear deformation and distinct transverse anisotropy, which are associated with folded structures originating from compression of the paleo-Tethys ocean accretional prism realigned by following shear deformation. The SGT receives lateral shear loading from its NS boundary and accommodates a right-step sinistral motion across the terrane boundary faults. The unique tectonic setting of the SGT defines locations and behaviors of internal faulting and strong earthquakes such as the 2021 Maduo earthquake, with the latter occurring on slow-moving faults at intervals of several thousands of years.
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Author contributions: H.Y. designed research; H.Y., Z.-K.S., Z.Z., T.W., B.C., Z.L., X.B., L.Z., Z.G., Y.Z., J.L.-Z., M.W., Q.H., S.Z., and L.X. performed research; H.Y. contributed new reagents/analytic tools; H.Y., T.W., B.C., Z.L., X.S., C.R., W.L., J.L.-Z., and M.W. analyzed data; and H.Y., Z.S., T.W., X.B., X.S., and J.L.-Z. wrote the paper.
Edited by Paul Tapponnier, China Earthquake Administration, Beijing, China; received September 6, 2021; accepted April 26, 2022
ISSN:0027-8424
1091-6490
1091-6490
DOI:10.1073/pnas.2116445119